South Dakota reservoir · state assessment record
Red Lake
Brule County. Assessment decisions reported by South Dakota to EPA under Clean Water Act sections 303(d) and 305(b), last assessed in the 2026 reporting cycle.
- 3,397
- Assessed acres
- Lake / Reservoir / Pond
- Water type
This waterbody in one line
Red Lake, a reservoir in South Dakota, is assessed as not supporting one or more designated uses, with one listed impairment cause in the state's most recent Integrated Report cycle (2026). By assessed acreage it sits among the largest 5% by assessed acreage nationally (38,628 lakes); its impairment list is among the longest nationally (one listed cause vs 23,610 assessed lakes). South Dakota assesses fish and wildlife propagation, recreation, and stock watering waters as not supported; it reported no verdict on aquatic life itself.
- Not Supporting
- overall status
- P98
- Assessed size nationally
- P20
- Shorter cause list
- Not Supporting
- aquatic-life or related
Assessment verdicts are the state agency's decisions as reported to EPA ATTAINS; PlainLakes renders them without modification.
A composite of this record's EPA ATTAINS designated-use verdicts, filed impairment count, and assessment currency, weighted and benchmarked against the national corpus of assessed active waterbodies. This is a water-quality standing, not a human-recreation or property-value judgment, and dimensions with no filed verdict drop out rather than count against the score.
Red Lake against the ATTAINS register
Paragraphs are selected by this unit's percentiles and use matrix: different lakes lead with different dimensions. Figures are ATTAINS / portal register arithmetic, not advice.
The signature stat: assessed size
The number that most separates Red Lake nationally is assessed size: 3,397 acres, larger than 98% of the 38,628 lake-type units with an area on file.
Every filed use falls short
On the uses this filer ruled on, aquatic life, every determination is Not Supporting. That is a use-by-use reading of the filed record, not a single overall lake grade.
Red Lake: Category 5, TMDL still owed
Category 5 is the Integrated Report band where a TMDL (or equivalent) is still expected for Red Lake. Read the listed causes and any cleanup actions filed beside them before treating the overall status tile as a finished restoration story.
Overall status: not supporting
The filer's overall status for Red Lake is Not Supporting. That tile summarizes the assessment unit; the designated-use rows and cause list are the evidence behind it.
Typical cause-list length
1 listed cause is a middle-tercile list length among assessed lake-type units. Look to IR category and use outcomes for the distinctive reading.
According to the U.S. Environmental Protection Agency's ATTAINS program, South Dakota carries 195 filed lake-type waterbodies in the August 2026 extract, and this page renders the assessment record EPA assigned to Red Lake without modification. See our methodology for reporting-unit limits and gauge linking rules.
The record
Designated-use assessments
Fully Supporting and Not Supporting are the state's definitive verdicts; other entries mean the use was not conclusively assessed in this cycle. South Dakota filed 2024 as the year this waterbody was last monitored. For the one definitive verdict on this record, South Dakota filed the assessment basis as Monitored Data. Those are EPA's own words, not PlainLakes' summary of them.
| Designated use | Group | Verdict |
|---|---|---|
| Fish and Wildlife Propagation, Recreation, and Stock Watering Waters | Aquatic-life or related | Not Supporting |
The record
Listed impairment causes
Causes the state listed as impairing designated uses of this reservoir, with the cycle each was first listed and the Clean Water Act action recorded against it.
| Cause | Affected uses | First listed | Cleanup standing |
|---|---|---|---|
| Mercury in Fish Tissue | Fish and Wildlife Propagation, Recreation, and Stock Watering Waters | 2026 | TMDL priority: Low |
Reading the record
Where Red Lake sits among peers
89% of South Dakota's lakes assessed this deeply also had no use supported
South Dakota ruled definitively on a single designated use at Red Lake and found it not supported. The dataset shows 27 South Dakota lakes judged to that same depth.
South Dakota's assessed lakes are most often judged on 4 uses; this one was judged on 1.
Computed share from EPA ATTAINS filed records, not an official EPA rating or safety grade.
| 1 | 2 | 3 | 4 | 5+ | |
|---|---|---|---|---|---|
| All supported | 3 | 7 | 0 | 26 | 5 |
| Mixed | Not possible | 1 | 0 | 84 | 10 |
| None supported | 24 (this record) | 8 | 2 | 16 | 0 |
Ringed cell: Red Lake. Source: EPA ATTAINS, Reporting cycles 1987–2026.
Scale and rank
Red Lake is one of 195 lake-type waterbodies reported to EPA from South Dakota, and one of 176 whose reported record carries enough populated assessment or gauge data for this site to list and index it. At 3,397 assessed acres it ranks 900th by assessed size among the 38,628 lakes the dataset carries an area for, counting a state’s repeated filings of one water once, behind 899 lakes with a larger one.
Open in the register
The state has not yet filed a definitive fish-consumption verdict and a definitive recreation verdict for this record; those fields populate when it reports them in a future Integrated Report cycle.
In context
Where Red Lake sits nationally
Assessed size among U.S. lakes
Distribution of assessed acreage across ATTAINS lakes filed with an area, counting a state’s repeated filings of one water once
3,397 Top 2% larger than 98% of 38,628 lakes
lakes the dataset carries an area for, counting a state’s repeated filings of one water once, bucketed by value
Source EPA ATTAINS · Reporting cycles 1987–2026
Listed causes vs waterbodies carrying a verdict
How many impairment causes U.S. waterbodies with a reported verdict carry
1 Longer than most more listed causes than 49% of 23,610 waterbodies carrying a verdict
named waterbodies carrying a verdict, bucketed by value
Source EPA ATTAINS · Reporting cycles 1987–2026
In both charts each bar is a band and taller bars hold more waterbodies; the dashed line and filled bar mark Red Lake. Hover or tap any bar for its full count and share.
In context
South Dakota context
ATTAINS carries 195 lake-type waterbodies in South Dakota, 145 assessed as not supporting at least one use and 41 fully supporting. Among the 176 indexed units there, Red Lake ranks 61st by listed-cause count (one listed cause) and 15th by assessed size among the 176 with an area filed; it sits in the not-supporting set (145 statewide) . Its listed causes include Mercury in Fish Tissue, which also appears among South Dakota's most-filed impairment causes (led by Mercury in Fish Tissue).
| Other large assessed lakes in South Dakota | Assessed acres |
|---|---|
| Lake Thompson Not Supporting | 13,888 |
| Lake Poinsett Not Supporting | 9,795 |
| Waubay Lake Not Supporting | 9,531 |
| Bitter Lake Not Supporting | 7,865 |
| Dry Lake Number 2 Not Supporting | 6,442 |
| Orman Dam (Belle Fourche Reservoir) Not Supporting | 6,106 |
Peers near Red Lake's size or cause load
Similar assessed acres
Nearest filed extents (3,397 acres here).
- Lake Ray Hubbard · 3,396 acres · TX
- Piscataquis River (1) · 3,406 acres · ME
- Lake Placid · 3,409 acres · FL
- Wawasee, Lake · 3,410 acres · IN
Similar cause load
Nearest listed-cause counts (1 here). Peers already in the acreage column are omitted.
- Aaron · 1 causes · MN
- Aaron River Reservoir · 1 causes · MA
- Abbotts Creek (including Lexington-Thomasville Water Supply Reservoir at normal reservoir elevation, Tom-A-Lex Lake) · 1 causes · NC
- Abeniki Lake · 1 causes · NH
What to do with this record
- Assessment verdicts are cycle-based, not real-time. For fish-consumption decisions, your state advisory program is the binding source. Consumption status guide
- Impairment listings follow the Clean Water Act 303(d) process; a listing is a regulatory finding, not a closure notice. 303(d) explained
PlainLakes renders state assessment decisions and federal gauge observations without modification. It does not issue advisories.
Assessment decisions on this page are rendered directly from state Integrated Report records in EPA's ATTAINS system; gauge figures are daily-value observations from the USGS National Water Information System, no number is typed in by an editor. Overall status, use verdicts, and causes are the state's reported decisions for assessment unit SD-MI-L-RED_01. Counts and percentiles are computed across all lake-type records PlainLakes ingests from ATTAINS. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of 2026-08-17. Primary sources: EPA ATTAINS and USGS National Water Information System.